S. pyogenes (Group A streptococcus) is an important human bacterial pathogen best known as the cause of skin and throat infections. Streptococcal infections vary in severity from relatively mild diseases, like impetigo and pharyngitis, to serious life threatening conditions such as septicemia, necrotizing fascitis, and streptococcal toxic-shock syndrome (Bisno and Stevens, 1996; Cunningham, 2000). Sequelae to S. pyogenes skin and throat infections include serious conditions such as acute rheumatic fever and post-streptococcal glomerulonephritis.
S. pyogenes expresses cell wall-anchored surface proteins with the ability to interact with abundant extracellular human proteins such as albumin, IgG, IgA, fibrinogen, fibronectin, and α2-macroglobulin (for references see Navarre and Schneewind, 1999). Many of these protein-protein interactions are mediated by members of the M-protein family.